Ozone is one of the most powerful oxidizers and disinfectants available. Ozone not only kills bacteria, but also inactivates many viruses, cysts and spores. In addition, ozone oxidizes many organic chemical compounds, including chloramines, soaps, oils and other wastes thereby rendering them harmless to the environment. Accordingly, ozone may be used for a number of purposes, including: drinking water purification, waste water treatment, air purification and sterilization, and a variety of medical uses. U.S. Pat. No. 4,250,040 to LaRaus, for example, discloses an apparatus using ozone to purify septic water. Similarly, U.S. Pat. No. 4,256,574 to Bhargava discloses the combination of ozone with a pure oxygen stream to treat sludge, and wherein part of the ozonation off-gas is reused to supply the oxygen requirement of the biological treatment.
Although ozone is especially beneficial for breaking down certain contaminants in water, obtaining a sufficiently high concentration in water to be effective is difficult for two reasons. First, it is difficult to economically and reliably generate large amounts of ozone. Second, it is difficult to infuse ozone into contaminated water at a sufficiently high dosage to achieve the full potential of ozone as a powerful oxidant.
Ozone is typically generated by one of two methods. Ultraviolet lamps operating at a wavelength of between 180-190 nanometers may be used to produce ozone in ambient air. Ozone may also be generated by creating an electrical corona discharge between two energized electrodes in ambient air or in another oxygen containing gas. The electrodes are typically separated by a dielectric material, such as a glass, or an air gap separation may be provided. The corona discharge is an ionization of the air and is visually indicated by the presence of a pale violet or bluish color in the area between and surrounding the electrodes.
Because ozone has a half-life of only about 22 minutes in ambient air before dissociating back to oxygen, a process requiring ozone must desirably have an ozone generator in relative close proximity to the intended point of application of the ozone. Thus, an ideal ozone generator is desirably compact, relatively simple in construction, consumes little electricity, and produces little waste heat while producing a high concentration of ozone.
A number of ozone generators have been made or proposed based on the electrical corona discharge process for producing ozone. In particular, a wide assortment of electrode configurations have been developed to try to improve the performance of the basic corona discharge ozone generator. In addition, an increase in ozone production efficiency may be obtained by cooling and drying the intake air for a corona discharge generator as shown, for example, in U.S. Pat. No. 3,884,819 to Schultz et al. Unfortunately, despite the numerous beneficial applications for ozone, there still exists a need for an ozone generator that is relatively compact, rugged, reliable, readily manufactured, energy efficient, and which produces a high concentration of ozone.
To increase the amount of ozone that is generated, ozone generating tubes have been combined into modular units as shown, for example, in U.S. Pat. No. 4,035,657 to Carlson, and U.S. Pat. No. 3,798,457 to Lowther. In addition, U.S. Pat. No. 4,138,724 to Kawauchi discloses a control system for a plurality of ozone generators and includes a computer for adjustably controlling the power delivered to the ozone generators in response to a predetermined program or a user input of ozone demand.
In certain applications, ozone has been combined with other oxidants or treatment means to achieve enhanced results. For example, the combination of ozone with ultraviolet light and hydrogen peroxide has been proposed for treating water containing hydrocarbons and/or hydrazine and hydrazine derivatives as disclosed, for example, in U.S. Pat. No. 4,849,114 to Zeff et al. In particular, the patent discloses treating contaminated water with ozone, hydrogen peroxide, and ultraviolet light simultaneously, or, alternately, first with hydrogen peroxide and ultraviolet light, followed by the addition of ozone.
Thus, despite the numerous benefits available from using ozone to decontaminate water, its use still presents a number of technical challenges particularly in generating ozone efficiently and also in effectively transferring the ozone into the water. While large scale commercial ozone generating systems are available, such systems typically have a high capital cost, require continuing maintenance, are physically too large and cumbersome, and are too energy inefficient to be readily adapted to many smaller potential industrial and commercial applications.